VAL-1221 to Treat Lafora Disease

Of all the intractable epilepsies, Lafora disease (LD) is among the most severe, and is inevitably fatal. There is no cure or therapy for LD and patients do not respond to antiepileptic drugs. Mutations in two genes have been identified that cause LD, EPM2A and EPM2B. Over the last 15 years, I have worked on LD, these genes, and their protein products by defining their cellular function and exploring putative therapeutic options. We and others have demonstrated that mutations in either of these genes cause glycogen to transform into malformed, aggregated inclusions called Lafora bodies (LBs). LBs are the etiological agent of LD, overtaking the cytoplasm of neurons and driving this progressive refractory seizure disorder. Importantly, multiple groups have shown that reduction of glycogen synthesis via genetic methods eliminates LB formation, eliminates seizures, and cures LD mouse models. Thus, an obvious treatment for LD is to decrease LB load in patients. Recent enzyme replacement therapy strategies utilize antibody fragments as a delivery platform that enables cell penetration. Our collaborators at Valerion Therapeutics fused a humanized antibody fragment to á-amylase, an enzyme that naturally degrades glycogen, to generate the VAL-0417 fusion. We designed a novel protocol for purifying large quantities of LBs from LD mouse models and found that VAL-0417 degrades LBs from brain, heart, and muscle tissues in vitro. We also found that VAL-0417 is active after intramuscular, intracerebroventricular, and intrathecal injection. Excitingly, VAL-0417 reduces LB load in vivo in LD mouse models. Thus, VAL-0417 is a promising therapeutic for Lafora disease with the potential of being the first drug to provide a clinical benefit. The goals of this project are: (1) Define the minimum effective dose of VAL-0417. In this Aim, we will define the minimum dose of VAL-0417 to efficiently degrade LBs in LD mouse models. (2) Determine the optimal in vivo dosing strategy. We will define the dose x duration versus response by performing a multi-day treatment experiment. A total of seventy 6-month old laforin KO mice and twelve WT mice will be implanted with Alzet osmotic infusion pumps containing either VAL-0417 or PBS for intracerebroventricular delivery. Animals will be sacrificed on days 4, 8, 15, 22, 29, and 60. This work will define the most efficacious dosing to gain LB clearance. We will also assess neuronal and glial viability via immunohistochemistry to determine if treatment efficacy correlates with disease progression. (3) Establish a noninvasive biomarker to assess treatment outcomes. We have already optimized a VAL-0417-specific enzyme-linked immunosorbent assay (ELISA) to monitor biodistribution. We have also initiated work to establish a noninvasive biomarker to monitor VAL-0417 activity during treatment. To date, we have optimized two assays to utilize as potential treatment monitoring tools, i.e. biomarkers. One methodology focuses on analyzing the oligosaccharides released from LBs by VAL-0417 and we have promising preliminary data for this methodology. The second is a mass spectrometry based method that monitors metabolite changes during treatment. We can accurately assign up to 800 metabolites involved in central carbon metabolism, glycogen metabolism, amino acid biosynthesis, pentose phosphate pathway, and nucleotide biosynthetic pathways. In preliminary experiments, we identified 22 metabolites that are up-regulated after VAL-0417 treatment and 48 metabolites that are down-regulated.